The present invention relates to a disc drive assembly. In particular, the present invention relates to an improved suspension design for supporting a head relative to a disc surface.
Disc drive systems are known which read data from a disc surface during operation of a disc drive. Such disc drive systems include conventional magnetic disc drives and optical disc drive systems. Optical disc drive systems operate by focusing a laser beam onto a disc surface via an optical assembly which is used to read data from the disc surface. Conventional magnetic disc drive systems use inductive type heads for reading or writing or magneto-resistive (M) heads for reading data. Discs are rotated for operation of the disc drive via a spindle motor to position discs for reading data from or writing data to selected positions on the disc surface.
Known optical assemblies include an objective lens which is positioned between the objective lens and the disc surface . The SIL is positioned very close to the data surface of the disc and is described in U.S. Pat. No. 5,125,750 to C. Orle et al., which issued Jun. 30, 1992, and in U.S. Pat. No. 5,497,359 to Mamin et al., which issued Mar. 5, 1996. In these optical systems, a laser beam is focused onto the SIL using an objective lens. The SIL is preferably carried on a slider and the slider is positioned close to the disc surface. Use of an SIL increases storage density.
The slider includes an air bearing surface to fly the SIL above the disc surface. The slider includes a leading edge and a trailing edge. Rotation of discs creates a hydrodynamic lifting force under the leading edge of the slider to lift the leading edge of the slider to fly above the disc surface in a known manner. The slider preferably flies with a positive pitch angle in which the leading edge of the slider flies at a greater distance from the disc surface than the trailing edge via a suspension assembly which includes a load beam and gimbal spring. The slider is coupled to the load beam via the gimbal spring. The load beam applies a load force to the slider via a load button. The load button defines an axis about which the slider pitches and rolls via the gimbal spring. The slider is preferably resilient in the pitch and roll direction to enable the slider to follow the topography of the disc.
The flexure of the gimbal spring permits the air bearing slider to pitch and roll as the slider flies above the disc surface. It is important to maintain the proximity of the SIL and slider relative to the disc surface to maintain the proper focus of light onto the disc surface as is known for optical disc drive systems. It is important that the flexure system including the load beam and the gimbal spring be designed to stably and accurately support the slider during operation of the disc drive system. In a magneto-optic (M-O) system, a magnetic transducer element is carried on the slider to write data to the disc surface. It is also important to accurately support and position the magnetic transducer elements relative to the disc surface during operation of an M-O system.
An actuator mechanism is coupled to the suspension assembly to locate the SIL relative to selected disc positions for operation of the disc system. During movement of the suspension system, force is transmitted through the load beam and gimbal spring to move the slider. Operation of the actuator mechanism, air bearing surface, and spindle motor introduce external vibration to the slider and suspension assembly. Depending upon the mass and stiffness of the suspension assembly, including the gimbal spring and load beam, external vibration may excite the load beam and gimbal spring at a resonant frequency. Thus the input motion or external vibration may be amplified substantially, causing unstable fly characteristics and misalignment of the slider relative to the disc surface.
External vibration or excitation of the suspension assembly and slider may introduce varied motion to the slider and suspension assembly. Depending upon the nature and frequency of the excitation force, the slider and suspension assembly may cause torsional mode resonance, sway mode resonance, and bending mode resonance. Torsional mode motion relates to rotation or twisting of the suspension assembly about an in-plane axis. Bending mode resonance essentially relates to up-down motion of the suspension assembly relative to the disc surface. Sway mode vibration relates to in-plane lateral motion and twisting. It is important to limit resonance motion to assure stable fly characteristics for the SIL. In particular, it is important to control the torsion and sway mode resonance, since they produce a transverse motion of the slider, causing head misalignment with respect to the data tracks on the disc surface.
The resonance frequency of the suspension assembly is related to the stiffness or elasticity and mass of the suspension system. Thus, it is desirable to design a suspension system which limits the effect of sway mode and torsion mode resonance in the operating frequencies of the disc drive while providing a suspension design which permits the slider to pitch and roll relative to the load button, and which has relatively high lateral rigidity and stiffness for maintaining precise in-plane positioning of the slider along the yaw axis.
It is also highly desirable to incorporate a deflection limiter in the design of the suspension assembly.
Deflection limiters are beneficial for several reasons. During a shock event, such as dropping the disc drive or HGA shipping tray, the mass of the head and lens can pull the gimbal away from the load beam if there is no deflection limiter. This deflection will induce stress in the gimbal. The stress could be high enough to yield the gimbal and result in dimple separation and changes to the pitch and roll static angle of the gimbal. A deflection limiter will prevent this from happening by ensuring that the deflection is not large enough to cause the stress to reach the yield point. Deflection limiters are also beneficial for ramp load/unload applications, especially with negative pressure air bearings.
Thus it is an object of the present invention to provide an improved suspension system for a disc drive. More specifically, it is an objective to provide an improved suspension design which utilizes a simplified design approach to providing a deflection limiter in a suspension system.
A further object of this invention is to provide an improved suspension which limits the resonance motion and the vertical travel of the gimbal to assure stable flying characteristics for the gimbal. More specifically, the objective of the invention is to limit the rotational or twisting motion of the suspension as well as the up-down motion of the suspension or gimbal relative to the disc surface.
These and other objectives of the invention are achieved by providing a gimbal spring which flexibly supports the slider relative to the disc surface. The design incorporates a base mounting portion which connects the gimbal spring to a load beam and thereby to the actuator of the disc drive which positions the gimbal and slider over a desired track on the disc. The gimbal includes opposed spaced flexure arms which are formed of elongated members, each having a proximal end and a distal end which define an opening therebetween, the proximal ends of the flexure arms being operably coupled to the base portion, and the distal end being cantilevered. A mounting tab is positioned between the ends of the flexure arms and supports the slider. Bridge sections are provided which connect the distal ends of the flexure arms to the mounting tab, the bridge sections extending at an angle relative to the flexure arms and being angled back toward the base section of the gimbal. More specifically, the bridges are curved to conform to the curvature of an optical lens mounted on the slider to be used to read information from or store information on the surface of the disc.
In a further feature, a deflection limiter is provided by defining a limiter comprising a continuous member extending across the width of the load beam tongue. The limiter extends over one surface of the load beam tongue; the opposite surface of the load beam tongue supports the slider. Preferably, the limiter extends from one section to the other so that the load beam is captured, and its vertical movement restrained, between sections and the limiter.
Another unique feature of this design approach is that it places the limiter and bond tongue towards the leading edge of the slider. This is beneficial for a ramp load/unload device since it will tend to lift the slider by the leading edge and prevent the leading edge of the slider from crashing into the disc as other gimbal/limiter concepts do that constrain motion at the trailing edge of the gimbal.
Other features and advantages of the invention can be found by reference to the attached drawings and accompanying description of an exemplary embodiment